For an LTE (Long Term Evolution) system and an LTE-A (Long Term Evolution-Advanced) system, in an uplink, a UL scheduler of a radio base station eNB is configured to select a transmission format in a PUSCH (Physical Uplink Shared Channel) in each TTI (Transmission Time Interval) and in each mobile station UE.
At this point, the transmission format includes a modulation system, a code rate, and the number of resource blocks. A TBS (Transport Block Size) is uniquely determined by the modulation system, the code rate, and the number of resource blocks.
The radio base station eNB is configured to notify the mobile station UE of the transmission format in the selected PUSCH using “UL grant” in a PDCCH (Physical Downlink Control Channel).
The mobile station UE is configured to transmit an uplink data signal through the PUSCH based on the transmission format of which the mobile station UE is notified through the PDCCH.
The UL scheduler of the general radio base station eNB estimates a PL (Path Loss) between the mobile stations UE, and selects the modulation system and the code rate such that the TBS is enlarged with respect to the mobile station UE having the small PL, thereby keeping a BLER (Block Error Rate) constant irrespective of the PL.
As a result, uplink throughput matching the PL is implemented, and system throughput can be increased while interference to another cell is suppressed.
The mobile station UE is also configured to determine a transmission power PPUSCH,c(i) in the PUSCH based on (equation 1) in FIG. 9.
Where “PCMAX,c (i)” is a maximum transmission power (after consideration of necessary power backoff) of the mobile station UE, “MPUSCH,c(i)” is the number of resource blocks, “Po—PUSCH,c(i)” is a power offset value (an annunciation parameter) that becomes a reference, “αc(j)” is an inclination parameter (an annunciation parameter) of Fraction TPC, PLc is a path loss, ΔTF,c(i) is a power offset value based on the modulation system and the code rate, and fc(i) is a closed-loop power control correction value.
The UL scheduler of the radio base station eNB selects the transmission format such that the transmission power PPUSCH,c(i) in the PUSCH of the UE becomes “PCMAX,c(i)” or less.
At this point, the UL scheduler of the radio base station eNB estimates the transmission power PPUSCH,c(i) in the PUSCH of the UE using (equation 1).
The BLER becomes larger than a target value, because the transmission power in the PUSCH of the mobile station UE is stuck to “PCMAX,c(i)” even if the UL scheduler of the radio base station eNB selects the transmission format in which the transmission power larger than “PCMAX,c(i)” is needed.
In the conventional LTE system and LTE-A system, a mechanism that feeds back “PHR (Power Headroom Report)” from the mobile station UE to the radio base station eNB is provided such that the UL scheduler of the radio base station eNB can select the proper transmission format.
At this point, the PHR is a report that reports a surplus transmission power PHtype1,c(i) of the mobile station UE. The surplus transmission power PHtype1,c(i) of the mobile station UE is obtained using (equation 2) in FIG. 10.
A term (1) in (equation 2) is the transmission power in the PUSCH in which the sticking of “PCMAX,c(i)” is not considered.
“PCMAX,c(i)” is a value in which an MPR (Maximum Power Reduction), an A-MPR (Additional-Maximum Power Reduction), or a P-MPR (P-Maximum Power Reduction) is subtracted from the maximum transmission power (or the maximum transmission power permitted/designated by a network) determined by performance of the mobile station UE.
At this point, the MPR or the A-MPR is a backoff value with respect to the maximum transmission power necessary to satisfy an adjacent channel interference provision.
In 3GPP TS36.101 (v10.0.0), a maximum allowance value of the backoff value is defined in the form of the modulation system, the number of resource blocks, a frequency band, and a position in the frequency band.
The P-MPR is a backoff value with respect to the maximum transmission power necessary to satisfy a SAR (Specific Absorption Rate) provision, which is newly introduced from an LTE-A system (that is, the LTE (Rel-10) system), and the like.
“SAR” defines an amount of energy absorbed in any tissue when a human body is exposed to an electromagnetic wave.
When the mobile station UE simultaneously performs transmission through two RATs (Radio Access Technologies), because an amount of radio wave generated from both the RATs needs to be considered, sometimes the SAR provision is satisfied only by the transmission power in one of the RATs, and possibly the backoff is performed to the maximum transmission power in the other RAT.
For example, in the case that sound communication through a cdma2000 system and data communication through the LTE system are simultaneously conducted, it is considered that the backoff is not performed to the transmission power in the cdma2000 system in order to maintain sound quality while the backoff is applied to the transmission power in the LTE system in order to satisfy the SAR provision.
At this point, because the sound communication through the cdma2000 system is a multi-rate, the backoff varies from moment to moment with respect to the transmission power in the LTE system when the transmission power varies from moment to moment.
In the LTE-A system, the mobile station UE is configured to transmit the PHR when a variation Δ in “PCMAX,c(i)” or a variation Δ in P-MPR, which is based on the P-MPR compared with a value in finally transmitting the PHR while “prohibitPHR-Timer” is interrupted, exceeds “dl-PathlossChange” (see FIG. 11).
The mobile station UE is configured to activate “prohibitPHR-Timer” when transmitting the PHR, and configured not to transmit the PHR until “prohibitPHR-Timer” is ended (see FIG. 11).
Specifically, in an example in FIG. 12, the mobile station UE is configured to transmit the PHR to the radio base station eNB at clock times t1 to t5.
At this point, the mobile station UE does not transmit the PHR, because the variation Δ does not exceed “dl-PathlossChange” although “prohibit PHR-Timer” is ended in periods A, B, and D.
The mobile station UE does not transmit the PHR, because “prohibitPHR-Timer” is not ended although the variation Δ exceeds “dl-PathlossChange” in a period C.